An often very important and central part of modern electric systems is a so called bus. Briefly described, a bus is a communication system or communication path that transfers data between different functional (or peripheral) units in a computer or between computers. Early buses consisted of parallel wires between different units, while today the term is used to describe all types of devices that distribute information between different functional units in a computer or between different units in an industrial system. To some context it can be said that the different functional units form different subsystems that are integrated into a larger bus system which enables data transfer, addressing, controlling, etc.
A common type of bus architecture has a plurality of functional units, so called modules, which are connectable to a common communication line and where each module has its own processing unit. Some modules may be provided with an input/output (I/O) interface in order to enable external units to communicate with the processing unit. These types of systems are for example used in various vehicles, such as cars. Modern cars are generally provided with a computer that monitors/oversees different aspects and functions of the car. The monitoring is often realized with the help of various sensors that provides information directly to the computer or other signals that indicate if a condition is true or false. Furthermore, modern cars often have a plurality of different subsystems such as breaking systems, airbags, cruise control, steering, lighting, windows, etc. and all of these are monitored and controlled by a computer. The communication path between these various subsystems and the computer, and also between the subsystems themselves, is then oftentimes provided by a bus.
An advantage with these systems or architectures is that the number and type of subsystems can be varied. For example, it is relatively simple to adapt the total system to specific applications and environments, updates and addition of functions is possible without the need of replacing the complete system, and also, maintenance and troubleshooting is facilitated since the subsystems can be isolated.
However, more and more problems are emerging due to rapid developments in computer technology during these last few decades and due to the need for larger subsystems, forcing the individual modules to handle more and more external units which consequently increase the amount of information that needs to be handled by the bus. The practical limitations of these buses are often related to their purely electrical contacts/connections, which have proven to be somewhat of a bottleneck in terms of bandwidth and efficiency.
An increasingly popular alternative to these electrical connections is to use optical solutions. Optical connections are generally associated with several advantages in comparison to their electrical counterpart, such as, e.g. improved bandwidth, reduced losses, robustness in terms of electromagnetic interference (EMI), etc.
There is however a number of problems and limitations associated with currently available optical buses. For example, they are oftentimes too expensive if they are to be as reliable as the electronic equivalent. Furthermore it has proven to be difficult to provide a relatively simple and cost-efficient (optical) architecture that fulfils requirements regarding speed and at the same time enables automatic addressing/positioning.